Method of refining hydrocarbon oil



B. K. ENGEL ET AL METHOD OF REFINING HYDROGARBON OIL Filed Dec. 8, 1945 'Jan-1s, 1949.

Patented Jan. 18, 1949 METHOD'OF `REFINING HYDROCARBON OIL Bruno Kuno Engel, Hoglandstorget, and Fredrik Teodor Emanuel Palmqvst, Stockhohn, Sweyden, assigfnors to `Aktiebolaget Separator-Nobel,

Stockholm, Sweden, a corporation of Sweden Application December 8, 1945, Serial No. 633,768

1 Claim. l This .invention :relates to 2a process 4for rening natural and thermally :pretreated mineral oils and mineral .oil .Iproducts by the aid of acid Areiining agents such Yas sulphuric facid, chlorosul- .phonic acid, luorosulphonic acid and others.

:Onelobjectiof the present :invention `is to 7provide Fa continuous l'reiining iprocess permitting the use of centrifugal `:separators :fitted with only two liquid` outlets. `Further objects 'are to carry out the refiningprocess 'with a :minimum of acid relining agent and in such a manner that the rai nate is substantially `free from acid compounds so `[that rit Ldoes not 1requireany `treatment with alkali.

Otheriobjeots '.of 'the inventionwill appear Afrom the following description.

It :has previously been suggested that mineral oil and mineral oil products Abe continuously refined by introducing `and mixing sulphuric acid intofastream of oil `and to conduct the mixture, after a certaintime of reaction, to a centrifugal separator Vin order to separate `the vrefined oil `from 'the acid and the undesirable hydrocarbons removed -by the acid. 'Infcarrying out `this -process, however, lcerta-in difliculties `have beenexperienced due tothe formation, in the centrifuge bowl, of three different liquid phases, viz. oil, acidsludge and water-diluted freeacid. -So as to permit continuous discharge of these ythree `liquid phases from the bowl., the latter has to be provided with three loutlets. :In Ypractice it has proved diilicult to :adjust these outlets `.satisfactorily for Acontinuous operation. Moreover, the dilute free lacidcftenl-oauses serious corrosion ci the centrifuge bowl and receptacles.

l Wehave disccveredthat whenadding sulphuric acid or other acid refining `agents to-mineralloils, an `extraction of the `more unstable components of the oil takes-placaas well as a reaction between these components andthe acid. At `this reaction water is `formed which diiutes the acid and redunes its `power of retaining the extractedhydrocarbons Aand yreaction products in solution. As the reaction proceeds, these compounds therefore partly separate from the acid solution, forming so-called acid sludgethebeforernentioned three liquid phases thus being obtained.` "Part vof the acid sludge isre-dissolve'din'theoil, thereby irn-` lpairing the quality of the raffinate. The latter contains 4*sulphonic acids and other yundesirable compounds, necessitating fanfalkali wash to obtain 'a 'satisfactory quality of the frafllnat-e.

By properly adjusting, according to thefpresent invention, Vthe temperature :and the time of the acid `treatment it has `.pmoved tpossibl'e to extract,

in-a preliminary step, the more unstable hydrocarbonsfand'to remove by centrifugal separation the acidnextractsolution from the oil, before water yielding reactions `take place to any substantial extent. Thus `dilution of the acid by reaction water and the resulting formation of a third liquid phase-is avoided, and in the centrifuge only two phases are separated, viz. oil and acid extract solution. The centrifuge bowl therefore has to bc provided `with two liquid outlets only, and the before-mentioned diiiiculties hitherto inherent with continuous 4operation are eliminated.

To ensure this, "the contact time in the preliminary extraction step has to be relatively short, and generally it should not exceed i minutes. For the same reason, 4the temperature ought to be relatively low, mostly below 20 C. and in some cases chilling `may have to be employed.

Thevamount of sulphuric acid or other acid refining agent should not be larger than required iorthe extraction, at the short Contact time indcated above and ywithdue regard to the mixing and contacting `equipment used, of at least the major portion -of the more unstable components of theoil--i e. those olenic, aromatic and hydroaromatic substances, whichreact relatively rapidly with the sulphuric acid during formation of reaction Water so that the majority of the non-4 paraiiinic hydrocarbons remaining in the oil are relatively `stable and can be subjected to a relatively prolonged action of sulphuric acid or other acid refining agent without any `danger of substantially water yielding reactions taking place.

When the more unstable or reactive hydrocarbonshave been .removed from `the oil bythis preliminary treating step, the oil is further treated for extraction of Athe remaining, mainly nonparanic hydrocarbons to be removed. This main treatment can be carried out in one or sevm eral steps by the aid of lknown extraction equipment. A suitable method is to feed oil and acid refining agent into a mixer and conduct the mixture, after a certain time of contact, to a centrifugal separator, where the acid extract so-l lution is removed from the oil. The latter may then once or several times again be mixed with acid refining agent and separated. Since water yieiding reactions may not be feared in these extract-ion steps, only two liquid phases are always obtained. viz. oil and acid extract solution, and the centrifuge bowls can be provided with two outiets fonly.

l It `has proved possible to reduce the sulphuric acid 'consumption considerably by `carrying out the extraction fincounter-current, i. e. by 4mining acid extract from a, later step with oil fed to a previous step. The content of extracted hydrocarbons in the acid extract is thereby gradually increased, and when the extraction is completed the extract can be subjected to a treatment for recovering the sulphuric acid and the extracted substances, respectively. This can be effected by adding water to the acid extract, thus splitting it into two phases, viz. on one hand dilute acid which may be concentrated e. g. by adding S03, and on the other hand a mixture of extracted hydrocarbons. The latter may also be dissolved by a suitable selective solvent, whereby the acid is directly recovered in a concentrated state.

'Ihe accompanying drawing forms a part of the specication and shows diagrammatically a prefer-red and practical embodiment of the invention.

The oil to be refined is fed through a pipe I into a mixer 2 where it is mixed with a small proportion of acid rening agent, e. g. sulphuric acid, entering the mixer through a pipe 3 and/ or 33. The quantity of acid used in this preliminary step amounts to maximum 30% of the total quantity of acid required, which varies according to the nature of the oil to be refined, the quality desired, the equipment used etc., between l and 20 partsusually -12 parts-of acid being required for 100 parts of oil. The temperature in the mixer 2 is kept below 20 C. and the time of contact amounts to 1 4.- minutes. Under these circumstances, an extraction of the more unstable components of the oil takes place, While water yielding reactions are substantially avoided. Thus only two phases are formed, viz. oil and an acid extract solution containing the unstable substances extracted from the oil.

From the mixer 2 the mixture is passed through a pipe 4 to a centrifuge 5 where theacid extract solution is separated from the oil and is discharged through a pipe into a tank 1. Through a pipe 3 water is added to the extract solution, causing two phases to be formed, viz. one oil phase and one phase consisting of dilute sulphuric acid with sulphonic acids dissolved therein. The recovered oil is discharged through a pipe 9 and can be used as fuel oil whereas the sulphuric acid solution, being drawn off through a pipe Iii, is

usually a lay-product of no value.

The pre-reiined oil from the centrifuge 5 is passed through a piping II to a second mixer I2 Where it is once more treated with sulphuric acid. Thence the mixture passes through a pipe I3 to a centrifuge I4 where the acid extract solution is separated from the oil and is discharged through a pipe I5. The oil is conducted through a pipe I6 to a third mixer I'I in which the acid treatment is repeated. IIhe acid-oil mixture passes through a pipe I8 to a centrifuge I9, from which the separated oil is taken through a pipe ZI] to a fourth mixer 2 I. I-Iere the final acid treatment takes place and the mixture flows through a pipe 22 to a centrifuge 23, from which the raffinate is discharged through a pipe 24.

The sulphuric acid is preferably passed in counter-current to the oil, as shown in the drawing, so as to obtain the best possible rening with a minimum of acid, fresh acid being used only in the last step, where the oil contains only a small amount of soluble hydrocarbons. In carrying out the process in that manner, the acid extract solution discharged from the fourth centrifuge-23 is conducted through a pipe 25 to the third mixer I'I, and from the third centrifuge l 9 the acid extract solution is then taken through the pipe 25 to the second mixer I2, to be finally discharged from the second centrifuge I4 through the pipe I5.

In continuous operation, the extract solution from the centrifuge I4 may be regenerated e. g. in a tank 21 in which the extract solution is treated with a solvent for the hydrocarbons, the solvent entering through a pipe 28. The hydrocarbon solution is drawn off through a pipe 29 and is taken to a distillation plant for recovering vthe solvent and the hydrocarbon extract, While the recovered concentrated acid is passed through a piping 30 and 3| to the last mixer 2I`. Fresh acid to make up for losses is supplied through a. pipe 32.

The acid can also be recovered by adding Water to the extract solution and concentrating the dilute acid thus obtained by means of S03 or evaporation.

From the pipe I5 the before-mentioned pipe 3 is branched on", part of the acid extract solution from the centrifuge I4 thus being conducted'to the primary mixer 2 to extract the more unstable components of the oil. The mixer 2 is also connected, by means ofthe pipe 33, to the fresh acid supply pipe 32 so that fresh acid can be used when starting up the plant. However, as soon as acid extract solution discharges from the centrifuge I4, only such solution should preferably be supplied to the mixer 2. In certain cases it may be of advantage to supply both fresh acid and acid solution to the mixer 2. i

When treating highly viscous oils it is advantageous to carry out the refining after addition of a diluent, which should preferably have a low viscosity and be of inert nature so that it is not attacked by the rening agent. The refining process can then take place at low temperature without excessive power consumption of 'the mixers and without undue reduction of the plant capacity and increase of the treating time,'respectively. As an example of a suitable solvent may be mentioned light parafiinic hydrocarbons or hydrocarbon mixtures in such a proportionpreferably Anot more than 25 %-that the viscosity of the mixture does not exceed '75 centistokes. rlhe diluent can be recovered-by means of distillation.- Y

By Ythe described process several advantages are obtained:

Only the relatively small amount of acid used in the preliminary treating step is obtained as a by-product of no value, whereas the acid used in the subsequent steps acts only as a vsolvent and can be substantially regenerated, which means a considerable saving of acid.

The formation of reaction water and the resulting splitting-up of the extract solution into acidsludge and free dilute acid is substantially avoided before and during the separation of the extract solution from the oil. The centrifugal separators used can thus be designed for separating two phases only, and the absence of reaction water reduces the corrosive action of the acid on the centrifuge bowls.

Reaction products, such as sulphonic acids etc-l, are not formed at all or are formed only to. a negligible extent prior to or duringthe separation. Consequently, the danger of such undesirable products being re-dissolved in the pre-refined oil-is eliminated or reduced so that the raflinate need not be treated-with alkali but has only to be subjected to af'bleaching process.

.'On account ofthe short contact time,` the treating tanks can be vrelatively small and the amount of oil tied up in the process is reduced accordingly.

As compared with the acid treating processes hitherto known, which do not involve any preliminary extraction of the more unstable components of the oil, the process according to the present invention insures either a better raffinate quality at the same yield, or a higher yield of rafnate with the same quality.

What we claim is:

The process of refining mineral oils and mineral oil products, which comprises continuously introducing, in a primary treating step, fresh and concentrated sulphuric acid into a stream oi oil to be rened, and in which primary treating step the acid is caused to act upon the oil at a temperature not exceeding 20 C. and during a period not exceeding four minutes, whereby by means of acid only the more unstable components of the oil are dissolved, while substantially inhibiting water yieldingreactions by the same', passing the oil and acid mixture through a locus of centrifugal force to separate the mixture into two phases, one of which is a pre-refined oil product Whereas the other is an acid solution of said more unstable components of the oil, and subjecting said pre- Number Name Date 1,959,712 Flowers May 2, 1934 1,975,987 Stratford Oct. 9,. 1934,

1,977,717 Davis et al Oct. 23, 1934 2,035,655 Jones Mar. 31, 1936 FOREIGN PATENTS Number Country Date 294,539 Great Britain July 20 1928 6 rened oil to a further treatment comprising a plurality of steps each of which involves addition of an `acid refining agent and in which the acid refining agent is caused to act upon the oil in counter-current thereto, each counter-current step involving centrifugal separation of the mixture into a refined oil product and an acid solution containing the less unstable soluble components of the oil. BRUNO KUNO ENGEL. FREDRIK TEODOR EMANUEL PALMQVIST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

